Claude Fable 5.1 and Mythos 5.1 are Anthropic's first models to watermark text outputs; a detection API is available to eligible groups as required under EU law (Ben Patterson/PCWorld) 01-09-2026

Ben Patterson / PCWorld:
Claude Fable 5.1 and Mythos 5.1 are Anthropic’s first models to watermark text outputs; a detection API is available to eligible groups as required under EU law — Anthropic has announced the arrival of its latest Claude models, and just as it promised last month, the new models will add invisible watermarks to all their text replies.